snow

This storm has a complicated setup. You have multiple surface lows within a broader upper-level trough, marginal surface temperatures, and large discrepancies in QPF placement between the models.

Temperatures along and east of I-95 are the most uncertain, which are expected to be in the low-to-mid 30s through most of the event. Areas north and west of I-95 will start above freezing, and will cool to at or below freezing depending on how strong the snowfall rates are tonight.

Snowfall rates will be one of the most important factors in determining which areas see 4-8 inches, and which areas get 1-4 inches. The best rates are likely to be along the Maryland/Pennsylvania border into southern New Jersey.

The intensity of the initial coastal low, the secondary coastal low development, the strength of the low over the Great Lakes, and the timing of the strengthening and weakening of these lows are wreaking havoc on the QPF output on the various models.

I tried my best to offer a realistic compromise between the differences in QPF, while also accounting for the surface temperature and snowfall rate issues. I could definitely see a tighter gradient between accumulation amounts than what I have on the map.

One final update before the frozen stuff starts to fall in the southwestern corner of my map. Made minor adjustments to the fringes in central/eastern North Carolina and up around NYC, with a slight expansion of the 18″+ contours.

Timing and impacts from this potential blizzard remain on track to what I said earlier today.

The heavy snow in the core of the Mid-Atlantic remains on track, given the newest model data and latest trends. Two notable changes were made to the northern and southern fringes of the snow accumulation. General timing remains the same, with snow expected to start in the D.C. area between 3-6 p.m. Friday.

The northeastern edge of the snow accumulation was cut back as confidence increases in the storm track, leaving lower snow amounts across northeastern Pennsylvania into northern New Jersey. On the southern edge, western North Carolina into western Virginia and West Virginia saw snow increases due to better confidence in the QPF forecast and better temperature profiles. Further east, more warm air wrapping into the eastern side of the system made for lower snow forecasts across northeastern North Carolina, southeastern Virginia, and along the immediate Atlantic Coast.

Ice will also be an issue in the Southeast and in southwestern Virginia. Currently, areas in northern South Carolina and central North Carolina are forecast to receive 0.25-0.75″ of ice, according to the NWS.

At the moment, the NWS also has Blizzard Watches posted from the greater D.C. region up through Philadelphia and into NYC and Long Island.

What can I say? This is a classic setup for feet of snow and possible/probable blizzard conditions across parts of the Mid-Atlantic. If you liked February 2010, then you’re gonna like this.

The epicness that is this storm system will start on Friday and end Saturday night/Sunday morning. For the greater DC area, I’m expecting snow to start accumulating in the late afternoon or early evening on Friday. Once it starts, it won’t stop for quite some time, lasting through Saturday in most spots.

Temperatures won’t be frigid, so I-95 and areas south should see more of a dense, wet snow, while areas further north and west get into the drier, fluffier snow. Mixing issues with sleet and rain don’t really become a problem until you get south and east of I-95. The I-95 cities are expected to be at or below freezing at the surface throughout the storm.

On top of all this, strong winds will generate blizzard or close to blizzard conditions mainly in the DC/MD/Delmarva region. Persistent onshore flow will result in fairly high storm surge and beach erosion.

Get home early on Friday, because you won’t want to be out once it starts. Don’t plan on doing anything that involves going outside Friday night or Saturday… unless it’s sledding or a snowball fight.

Can this be the last one, please? Near normal highs are going to feel like heat waves this month.

Most uncertainty is going to come from the changeover from rain to sleet to snow. A slower cold push and/or prolonged sleet could cut down on totals. Regardless of the fact that there’s more downside than upside, it should be a fun storm. Once the changeover to snow does occur, the snow rates should be pretty good, so I’m not too worried about getting accumulations started in the more southern areas when the changeover isn’t until after sunrise. A layer of sleet to start should help the initial snow accumulations as well.

It’s time for the southern folks to finally cash in this season. Some spots in North Carolina and southeastern Virginia are expected to get as much snow as they typically get in a year, so this should be a fun storm for them. I battled a bit in the placement of the 1″ and 2″ contours on the north edge of things, as there is a wide range of solutions in that department still. The rain/snow line across North Carolina is another big hurdle, but it seems the warm nose will be around 850mb, which made sorting it out on the models easier.

I expect a couple of 12+” reports out of this in North Carolina and southeastern Virginia. The northern edge of the 1-2+” has equal risks of busting high/low.

Lots of uncertainty with this system. How much precip. falls as snow before the changeover, timing of the changeover, rates during the daytime hours, etc. The only thing that’s not really in question will be the surface temperatures at the start of the storm. Cold, cold, cold.

Models overall show a little more potential to get higher totals than lower totals east of the Appalachians.